(539e) Hybrid Membranes Based on Functionalized Metal-Organic Molecule Nanocages for Efficient Aromatic Hydrocarbons Recovery

Hybrid
Membranes based on Functionalized Metal-Organic Molecule Nanocages for
Efficient Aromatic Hydrocarbons Recovery

Cui Zhao, Naixin Wang, Lin Wang, Shunan Sheng, Shulan Ji*, Jian-Rong Li*

Beijing Key Laboratory for Green Catalysis
and Separation and Department of Chemistry and Chemical Engineering, Beijing
University of Technology, Beijing 100124, P. R. China.

The development of efficient and economic
technology to separate aromatic hydrocarbons from their aliphatic mixtures has
been of great concerns in chemical industry. Among them, the membrane-based
separation has been recognized as one of the most promising approaches in
aromatic hydrocarbons gathering.[1,2] However, the challenge for this membrane
separation technique is the selection/preparation of high quality membranes
with good selectivity and permeability.

Recent years, inorganic-organic hybrid
membranes have gained urgent attention in the membrane separations.[3-6] Where,
the unique nature of the inorganic fillers and their good dispersion and
compatibility in/with the polymer are crucial for the separation performances
of this type of membranes. Therefore, in order to solve the dispersion and
uniformity problems, and at the same time to efficaciously control their
loading in polymer, herein, our strategy is to use soluble metal-organic
polyhedra (MOPs) molecules as fillers to prepare hybrid membranes, exemplified
as below.

A nano-hybrid membrane with soluble MOP-tBu, [Cu₂₄(5-tBu-1,3-BDC)₂₄(S)₂₄]
as fillers was initially fabricated by adopting the typical co-blending method,
and used in the pervaporation separation of aromatic/aliphatic
hydrocarbons.[7,8] It was found that this membrane is interfacial
defect-free and homogeneous, and shows excellent performance for the toluene/n-heptane separation with a high total
flux of 229.5 g/m² h and a separation factor of 19.0; while for the
benzene/cyclohexane separation with a high total flux of 392.3 g/m²
h and a separation factor of 15.39 at 40 °C. More remarkable, this MOP-based
hybrid membrane had long-term stability in its performance in separating
aromatic/aliphatic mixtures (see Figure. 1).

Furthermore, in order to improve the
separation of aromatic/aliphatic hydrocarbons, a series of isostructural
functionalized MOPs/hyperbranched polymer Boltorn W3000 membranes are
molecularly designed and fabricated by a new method, which helps plugging the
pores within the substrate.[9] Pervaporation tests employing these MOP-X (X =
SO₃Na, OH, and tBu) filled
hybrid membranes demonstrated an significant improvement for the aromatic
hydrocarbons separations. Particularly, the membrane with MOP-SO₃Na
showed the highest permselectivity for a toluene/n-heptane mixture. Simultaneously, adsorption experiments and
molecular simulations also confirmed that stronger polar functionalized groups
have higher adsorption capacity towards the aromatic hydrocarbons, being in
agreement with pervaparation experiments results.

Overall, in light of the
versatile structures and customizable chemical functionalities of MOPs
materials, a lot of hybrid membranes can thus be fabricated for different
separation applications, after paving the road in this work.

Keywords:
hybrid membrane, metal-organic polyhedra, pervaporation, aromatic/aliphatic
hydrocarbons separation

References

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[9]
C. Zhao, N. Wang, L. Wang, S. Sheng, S. Ji and J.-R. Li, Functionalized
Metal-Organic Molecule Nanocages Filled Hybrid Membranes for Effective Aromatic
Recovery: Further Analysis by combining Adsorption Experiment and DFT
Calculations, submitted.

Figure 1.
Pervaporation performances of MOP-tBu/W3000
nanohybrid membrane and a comparison of pervaporation performances of some
reported hybrid membranes towards the separation of toluene/n-heptane mixture.